The invention relates to the field of stereoscopic displays in general and more particularly to digital processing done on the stereoscopic images to be projected.
Stereoscopic 3-D imaging requires the presentation of two slightly different sets of images to a viewer, one set corresponding to a left eye viewpoint and the other corresponding to a right eye viewpoint. When the sets are presented so that only the left eye of a viewer can see the left eye set of images and only the right eye can see the right eye set of images, the viewer will be able to perceive a 3-D image.
When a common display for both eyes is used, three methods are usually used to ensure that only the set of right eye images is seen by the right eye and only the set of left eye images is seen by the left eye. The first method is to project both sets of images in different colors and to make the viewer wear glasses which filter the appropriate colors to show different images for each eye. The colors that are mostly used are red and blue. The main disadvantage of this method is that the resulting 3-D images are deficient in color information.
The second method is to use polarized images and polarizing glasses. Each lens of the glasses has a polarized filter which corresponds to a direction of polarization of the polarized images projected. The axes of polarization are usually 90 degrees apart. Two projectors are used with polarization filters corresponding to the axes of the filters on the lenses. The images are shown simultaneously but each eye sees a different image. The major disadvantage of this method is that the quality of the 3-D effect decreases substantially as the viewer tilts his or her head to either side.
The third method uses shutter glasses and multiplexes the sets of images in time. Liquid crystal display (LCD) shutter glasses are used to alternately display left eye and right eye images to a viewer in order to provide the illusion of 3-D. Since the viewer looks at a single video monitor which displays alternately left eye and right eye images, every other frame, in synchronism with the switching of the shutter glasses, the video screen must respond quickly to the switching from one image to the other. Otherwise, there is some blurring of the left image with the right image seen by the wearer of the glasses. This blurring is often referred to as xe2x80x9cghosting effectxe2x80x9d, xe2x80x9ccross-talkxe2x80x9d or xe2x80x9ccross-imagesxe2x80x9d. The delay in a refresh of the video screen has to do with the specific phosphorus used and is a difficult parameter to control.
U.S. Pat. No. 5,402,191 describes an improvement of the LCD scattering shutter using light scattering to help eliminate crosstalk. This method improves the quality of the LCD""s, but it does not eliminate the ghosting effect completely because the computer monitor""s picture tube or cathode ray tube (CRT) uses phosphor to convert the cathode rays into visible light. These phosphors retain a glow from one frame to the next. As mentioned in U.S. Pat. No. 5,402,191 at column 2, lines 48 through 52, the alternating left-eye frames and right-eye images are displayed in succession. So, when the monitor draws the right-eye image, the monitor""s phosphor still retains a bit of light from the previously displayed left-eye image.
Even if the LCD shutters were absolutely perfect and did not allow any light through when blocking out the appropriate image to the appropriate eye, when the shutter opens to show the successive image, there is still a dim image retained from the previous eye-image by the monitor""s phosphor. To the viewer, there appears to be a ghost in the image which is really the alternate image for the alternate eye. This ghosting effect is very tiring for the eyes of the viewer and, when the systems are used for prolonged periods of time, they are known to cause headaches and blurring of the viewer""s vision.
Other existing techniques for eliminating the xe2x80x9ccrosstalkxe2x80x9d are usually improvements in either the display technology (e.g. laser displays), for example in U.S. Pat. No. 5,781,229, or use multiple displays, a monitor for each eye, for example in U.S. Pat. No. 5,936,663. These techniques are very expensive and require new equipment.
Most prior art techniques deal with new methods of alternating the left-eye and right-eye images in succession to eliminate the ghosting effect. These techniques have not proven to completely eliminate the ghosting effect.
There is a need for a system for viewing images in 3-D which eliminates cross-talk between left- and right-eye images.
Accordingly, an object of the present invention is to provide a method for eliminating the ghosting effect present when viewing 3-D images on a screen.
Another object of the present invention is to provide a 3-D projection system which permits the user to enjoy viewing 3-D images for a longer period of time.
Another object is to eliminate crosstalk between 3-D images using existing equipment.
Another object of the present invention is to eliminate crosstalk while keeping the projection apparatus at a low price.
Another object of the present invention is to modify the successive images to compensate for image leakage between the eyes, such as the retained image by the phosphor glow of the CRT in the case of shutter glasses, shutter inefficiency, polarizer inefficiency in the case of polarized displays, or filter inefficiency in the case of color separation.
In accordance with a first aspect of the present invention, there is provided a method for eliminating a ghosting effect in images to be viewed in 3-D, the method comprising creating a left source image and a right source image, compensating said left source image and said right source image for image leakage to obtain a compensated left image and a compensated right image, displaying said modulated compensated image.
Another method is provided wherein said step of compensating said left source image and said right source image comprises creating a compensated left image by taking a first percentage of said left source image and subtracting a second percentage of said right source image, creating a compensated right image by taking a third percentage of said right source image and subtracting a fourth percentage of said left source image.
Another method for eliminating a ghosting effect in images to be viewed with a 3-D stereoscopic apparatus, the method comprising creating a left source image and a right source image, modifying the left source image using information from the right source image, modifying the right source image using information from the left source image, displaying the compensated left image and compensated right image on a common display in a manner enabling 3-D viewing and wherein a viewer sees a 3-D stereoscopic image of the left and right images with reduced cross image.
Another method is provided for calibrating the compensation done on source images to be displayed in 3-D on a common display, the method comprising providing an adjustment for at least one parameter of the proportion of the left eye image and the proportion of the right eye image, obtaining a user input with respect to the image displayed, using the user input to calibrate the compensation done on the source image.
Another method is provided in which the parameter comprises a proportion of white.
Another method is provided in which the calibration of the compensation is done for each eye.
An apparatus for eliminating the ghosting effect present when viewing 3-D stereoscopic images is also provided, the apparatus comprises an image editor and composer for creating left and right source images, an image compensator for creating left and right compensated images, a display apparatus for displaying the left and right compensated images in a manner enabling 3-D viewing.
Another apparatus is provided in which the image compensator comprises a first adder, a second adder, a first mixer and a second mixer wherein a proportion of the left source image is added in the first adder to a positive or negative proportion of the right source image calculated by the second mixer, a proportion of the right source image is added in the second adder to a positive or negative proportion of the left source image calculated by the first mixer and whereby a compensated left image and a compensated right image are produced. White can also be added to the images to better compensate for the ghosting effect.
In accordance with another aspect of the present invention, there is provided an electronic medium on which is recording data corresponding to a software module which, when loaded in a computer and executed, carries the steps of a method according to the present invention or constitutes an apparatus according to the present invention.
Another apparatus is provided for calibrating the compensation done to eliminate the ghosting effect present when viewing 3-D stereoscopic images. The apparatus comprises an image editor and composer for creating left and right source images, an image compensator for creating left and right compensated images, a display apparatus for displaying the left and night compensated images in a manner enabling 3-D viewing, a compensation selector for selector an appropriate calibration of the compensation and a user input interface for entering the user selection for the compensation. The compensation factor selected is then sent to the image compensator which uses it to compensate the left and right source images.
In accordance with another aspect of the present invention, there is provided a method for eliminating a ghosting effect in images prepared for 3-D viewing by a 3-D stereoscopic apparatus. The method comprises obtaining a source image stream containing alternating left source images prepared for 3-D viewing and right source images prepared for 3-D viewing, buffering the source image stream by a delay of one image, using the buffered source image stream and the source image stream to obtain the corresponding left and right source images, modifying the left source image using information from the right source image to create a compensated left source image, modifying the right source image using information from the left source image to create a compensated right source image, displaying the compensated left image and compensated right image on a common display in a manner enabling 3-D viewing and wherein a viewer sees a 3-D stereoscopic image of the left and right images with reduced cross image.